I am presently using Wordpress to operate this site. However, with every era I are more worried about software bloat and also the convoluted table structures accustomed to store my data. Maybe this can be a fruitless pursuit. Features will always be put into blogging software until it claims to become a Content management systems--and at that time your computer data is most likely stuck.
You have a choice of adhering using the 2. branch. This is maintained with only bug fixes until 2010. Have a look at http://wordpress.org/download/legacy/
I additionally sometimes be worried about the big changes WordPress undergoes.
However, since all of the important data (the posts themselves and also the comments) are saved inside a database, it doesn't appear hard to extract them just in case of need (moving to another system, or simply backup). Even when the table structure will get more complicated, the MySQL DB WordPress uses is easily accessible and extract data from.
I am certain you can easily find such extractors freely floating within the web.
Wordpress comes with an 'export' feature. It downloads the majority of the data for example posts, pages and comments within an XML file. These XML files could be imported into other Wordpress installations.
You may also produce a simple importer to import that data else where.
No previous solutions have really addressed the title of the question.
How if the tables be built for any blog? That entirely is dependent on what you would like related to it, honestly.
One approach would be to possess a posts table along with a comments table. The posts table might have the title, content, date, along with a publish id. Your comments ought to table will have a publish id, comment id, commenter note, and content.
But that is really only relevant if you are building it yourself. No blogging tools I've ever seen are extremely inefficient when it comes to space usage, and every one of them provide import tools from "standard" formats (from blogger, wordpress, moveabletype, etc to the where else). Also keep in mind that they'll all publish posts and comments via RSS, causing them to be eminently portable.
WordPress particularly continues to be only one.2 Megabytes like a tar.gz. If that is large enough to stress about bloat, I'd highly recommend building one yourself, or moving to some located blogging service :)